472290 A7 B7 五、發明說明（丨） 本發明之領域 本發明係有關於用於工件的離子植入之電漿摻雜系統 ，並且更特定地有關於一種用於電漿摻雜系統的陰極幾何 形狀。 本發明之背景 離子植入是一種用於導入改變導電度的雜質進入到半 導體晶圓中之標準的技術。在一種習知的離子植入系統中 ’ 一種所要的雜質材料係在一個離子源中被離子化、該些 離子係被加速以形成一具有預定的能量之離子束、並且該 離子束係被導向晶圓的表面。在該束中活躍的離子係滲透 進入到大部分的半導體材料中，並且被嵌入到半導體材料 的晶格中，以形成一個具有所要的導電度之區域。 嚴格的要求係被加諸在關於被植入到該晶圓中之累積 的離子劑量、植入深度、橫過晶圓表面的劑量均勻性、表 面損傷以及不要的污染之有關離子植入的半導體製程之上 。被植入的劑量與深度係決定被植入的區域之電氣活動， 而劑量均勻性是必要的，以確保在該半導體晶圓上的所有 元件具有在所指定的限制之內的操作特性。過度的表面損 傷’尤其是化學蝕刻，或是表面的污染可能會毀壞在該晶 圓上先前製作的結構。 在某些的應用中，在半導體晶圓中形成淺接面是必要 的’其中該雜質材料係被限制在一個靠近該晶圓的表面之 區域處。在這些應用中，習知的離子植入器之高能量的加 速以及相關的束形成硬體並非必要的。於是，已經提出來 3 本紙張尺度適用中國國家標準（CNS)A4規格（2〗〇 X 297公釐） (請先閱讀背面之注意事項再填寫本頁) 裝-----r---訂---------線 經濟邰智慧W產局員工消赀合作社印製 472290 A7 B7 五、發明說明（-/) 使用一種用於在半導體晶圓中形成淺接面的電漿摻雜 (PLAD)系統。 (請先閱讀背面之注意事項再填寫本頁) 在一種PLAD系統中，一個半導體晶圓係被置放在位 於一室中之導電的平台上，並且該平台作用爲—個陰極。 一種含有所要的摻雜物材料之可離子化的氣體係被導入到 該室之中’並且一個局電壓脈衝係被施加在該平台與該陽 極（或是室壁）之間’此係使得一具有電漿鞘的電漿在該晶 圓的附近產生。所施加的電壓係使得電漿中的離子穿過該 電漿鞘並且被植入到該晶圓之中。植入的深度係有關於被 施加在該晶圓與該陽極之間的電壓。一種電漿摻雜系統係 在1994年10月11日核准公告授予Sheng的美國專利案號 5,354,381中加以描述。 經濟部智慈財產局員工消t合作社印製 在上述的PLAD系統中，該高電壓脈衝孫產生該電漿 並且從該電漿加速正離子朝向該晶圓。在其它類型的電漿 植入系統中，以電漿源的離子植入(PSII)系統著稱，一個別 的電漿源係被利用來提供一連續的電漿、。（這些植入系統也 以數種其它的頭字語著稱，最普遍的是電漿浸入式離子植 入，ΡΙΠ)。在此種系統中，該平台以及晶圓被浸入到此連 續的電漿中，並且在間隔下、一個高電壓脈衝係被施加在 該平台與該陽極之間，使得電漿中的正離子被加速朝向該 晶圓。此種系統之一例子係在1988年8月16日授予 Conrad之美國專利案號4,764,394中加以描述。 PLAD系統優於PSII系統之一優點是在於該電漿只有 在該目標物體被植入時才會導通。此導致因爲該PSII系統 4 尺度適用中國國家『票準（CNS)A4規格（2.丨〇 X 297"¥"髮~) 472290 A7 B7 五、發明說明（>]) 之連續的電漿所產生之化學活性的物種之減少，因而減少 對於該晶圓表面之化學損傷。此外，該連續的電漿也可能 引起高程度之被植入的污染物以及高程度之微粒子形成。 該PLAD系統係藉由除了當該目標物體被偏向以植入離子 時之外、都關斷該電漿來改善該PSII系統。此係降低污染 物、微粒子以及表面蝕刻損傷的程度。 PLAD系統係具有一個最小的崩潰電壓Vbd，在該電 壓Vbd之下電漿係啓動，因而離子可以被植入。此崩潰電 壓Vbd係由該系統的物理特性所界定，其包含有該陰極的 表面材料、存在該系統中的氣體類型、在該系統中的氣體 壓力P以及從該陰極至陽極的距離d。對於一種特定的表 面材料以及氣體類型，該崩潰電壓曲線Vbd是P X d的函數 ，並且以Paschen曲線著稱。該過程充分描述於電漿物理 的教科書中。典型地，該崩潰電壓Vbd之最小的値是接近 Pd与500毫微托-公分。對於BF3，一種用於Si的PLAD之 常見的饋入氣體而言，該最小的崩潰電壓Vbd与-530V。其 它的摻雜物饋入氣體/基板之組合都將具有類似的最小的崩 潰電壓Vbd。在習知技術的PLAD系統中，電漿中的離子 之植入能量是直接成比例於該陰極至陽極的電壓。 在PLAD系統中，至該陰極的離子電流是所施加的電 壓、氣體壓力以及表面情況的函數。對於接近Vbd的電壓 而言，該電流是低的。當該電壓或是該壓力被增加時，該 電流係增加。爲了增加電流且因而減少植入的時間，運作 在更高的壓力以芨超過Vbd的電壓下是所期望的。區域的 5 (請先閲讀背面之注意事項再填寫本頁) —裝-----^—訂---------線 經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家標準（CNS)A4規格（2]0 X 297公釐） 472290 經濟部智慧財產局員工消赀合作杜印製 A7 B7 五、發明說明（W ) 表面情況、表面溫度、材料、材料結構(晶體的相對於非晶 體的）、等等，也在區域的離子電流上扮演相關的因素。 爲了增加生產速率，亦即，增加通過該摻雜製程之目 標晶圓的產出量，處理每個晶圓所花費的時間需要被減少 。如同已知的，對於一個目標晶圓之循環時間係包含抽真 空該室所需的時間、導入該摻雜物的饋入氣體並且將該室 成爲所要的壓力所需的時間、以及用離子電流轟擊該目標 晶圓來完成所要的摻雜物密度之程度所需的時間長度。因 此，需要一種方式來改善利用一種PLAD系統之生產速率 以及均勻性。 本發明之槪要 根據本發明之第一特點，一種脈衝的電漿處理系統係 被提供。該系統係包括一個陽極；一個目標陰極，其上將 被置放一第一目標，該目標陰極係與該陽極間隔開並且被 定位與該陽極大致上爲平行的；以及一個中空陰極，其係 被設置相鄰於每個該陽極以及該目標陰極。該中空陰極係 圍繞在該陽極與該目標陰極之間的空間之一部份。 該系統更包括一個具有一輸出的第一高電壓脈衝源， 其中該陽極係被耦接至一個參考電壓；並且該目標陰極以 及該中空陰極係分別連接到該第一高電壓脈衝源的輸出。 在本發明的另一特點中，該系統係包含一個具有一第 一輸出的第一咼電壓脈衝源以及一個具有一第二輸出的第 二高電壓脈衝源。該陽極係被耦接至一個參考電壓；該目 標陰極係被耦接至該第二輸出；並且該中空陰極係被耦接 6 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公楚） (請先閱讀背面之注意事項再填寫本頁) 丨-----：----訂----1----線 472290 A7 B7 五、發明說明（$ ) 至該第一輸出。 在本發明的另一特點中，一種脈衝的電發處理系統係 被提供。該系統係包括一個外殻；一個被設置在該外殻之 中的陽極，該陽極以及外殻係耦接至一個參考電壓；一個 目標陰極，其上將被置放一個第一目標，該目標陰極係被 設置在該外殻之中、與該陽極間隔開並且被定位與該陽極 大致上爲平行的；一個被設置在該外殼之中並且相鄰於每 個該陽極以及該目標陰極的中空陰極，該中空陰極係圍繞 在該陽極與該目標陰極之間的空間之一部份；以及—個 接到該目標陰極以及該中空陰極的高電壓脈衝源。 在本發明的又一特點中，一種在一脈衝的電漿處理系 統中植入離子於一個第一目標中之方法係被提供。該方法 係包括提供一個陽極；定位一個陰極與該陽極間隔開並且 與該陽極大致上爲平行的；設置該第一目標在該陰極之上 ;定位一個中空·陰極相鄰於該陽極以及該陰極’並且在該 陽極以及該陰極之間；並且施加一個第一高電壓脈衝至該 中空陰極，其中該中空陰極係圍繞在該陽極與該目標陰極 之間的空間之一部份。 在仍是本發明的另一特點中，一種脈衝的電漿處理系 統係被提供，其係包含一個第一陽極；一個第二陽極’其 係與該第一陽極間隔開並且相對於該第一陽極；一個被設 置相鄰於該等第一與第二陽極的中空陰極，該中空陰極係 圍繞介於該第一與第二陽極之間的空間；以及一個第一阔 電壓脈衝源’其係相對於一個參考電壓供應一個正電壓脈 7 (請先閱讀背面之注意事項再填寫本頁) -裝 丨訂---------線 經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐） 經濟部智慧財產局員工消f合作社印製 472290 A7 B7 五、發明說明（b ) 衝至每個該等第一與第二陽極；其中該中空陰極係被耦接 至該參考電壓。 圖式之簡要說明 爲了更加瞭解本發明，該附圖係被參考，其中相同的 參考圖號係指相同的元件，並且其中： 圖1是習知的電漿摻雜系統之槪要的方塊圖； 圖2A是本發明之第一實施例的槪要圖； 圖2B是沿著圖2A中的線2B-2B所取之圖2A的橫截 面； 圖3A是本發明之第二實施例的槪要圖； 圖3B是沿著圖3A中的線3B-3B所取之圖3A的橫截 面； 圖4A是本發明之第三實施例的槪要圖； 圖4B是沿著圖4A中的線4B-4B所取之圖4A的橫截 \ 面； 圖5是利用雙PLAD脈衝的本發明之橫截面槪要圖； 並且 圖6是利用一個正PLAD脈衝的本發明之橫截面槪要 圖。 午要部份代表符號之簡要說明 10電漿摻雜室 12封閉的容積 14平台 20半導體晶圓 8 (靖先閱讀背面之注意事項再填寫本頁) 裝-----^---訂---- 線 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐） 經濟部智慧財產局員工消f合作社印刹^ 472290 A7 _B7__ 五、發明說明（1 ) 24陽極 26箭頭 3〇高電壓脈衝源 32可控閥 34真空泵 36氣體源 38質量流控制器 40電漿 42電漿鞘 44壓力感測器 46控制器 50量測元件 70劑量處理器 130第二高電壓脈衝源 300中空的圓柱形陰極 300’矩形中空陰極 302、302-1、302-2平面的陰極 304、304-1、304-2平面的陽極 400環形陽極 詳細說明 習知的電漿摻雜系統之一實例係槪要地在圖1中加以 顯示。一個電漿摻雜室10係界定一個封閉的容積12。一 個被定位在室10中的平台(陰極）14係提供一個用於支承一 例如是半導體晶圓20之工件的表面。半導體晶圓只是可能 9 本紙張尺度適用中國國家標準（CNS)A^規格（210 X 297公釐） (請先閱讀背面之注意事項再填寫本頁) -裝--------訂----- 線 經濟部智慧財產局員工消費合作社印製 472290 A7 _ B7 五、發明說明（X) 的目標類型之一實例。本發明並不限於只有在半導體晶圓 中植入離子。例如，離子植入在用作工具的金屬、汽車組 件、衝模、以及塑膠中也是可能的。例如，該晶圓20可以 在其週邊被夾到平台14的平坦表面。該平台μ係支撐晶 圓2〇並且提供電氣連接至晶圓2〇。在一種版本中，該平 台14係大致上爲平面的並且具有一個用於支撐晶圓20的 電氣導電的表面。在另一種版本中，該平台14係包含用於 電氣連接至晶圓20之導電的銷。 在與該平台（陰極）H間隔開的關係下，一個陽極24 係被定位在室10中。陽極24可以在由箭頭26所指的垂直 於平台14之方向上移動。該陽極24係典型地連接到該室 10之電氣導電的壁，兩者都可以連接到接地。在一種版本 中，該陽極24以及平台14係大致上彼此爲平行的。 該晶圓20以及該陰極14係被連接至一個高電壓脈衝 源30，因而晶圓20作用爲一個陰極。該脈衝源30係典型 地提供在大約100至10,000伏特的範圍內、大約1至50 微秒的持續期間並且在大約100Hz至2KHz的脈衝重複率 之下的脈衝。將理解的是，這些脈衝參數値僅是藉由特定 的舉例而已，而其它的値係可被利用。 室10之封閉的容積12係透過一個可控閥32而被耦 接至一個真空泵34。一個氣體源36係透過一個質量流控 制器38而被耦接至室1〇。一個位在室1〇中的壓力感測器 44係提供一指示室壓力的信號至一個控制器46。該控制器 46係比較所感測到的室壓力與所要的壓力輸入，並且提供 10 -------------裝-----^--^丨訂--------線' (請先閱讀背面之注意事項再填寫本頁) 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公楚） 472290 A7 ___—--- B7_ .一 五、發明說明（彳） 一控制信號至閥32。該控制信號係控制閥32以便於將介 於該室壓力與所要的壓力之間的差異最小化。真空泵34、 閥32、壓力感測器44以及控制器46係構成一個閉迴路的 壓力控制系統。該壓力係典型地被控制在大約1毫拖耳 (mtorr)至大約500毫拖耳的範圍中，但並不限於此範圍。 氣體源36係供應一種含有用於植入到該工件中之所要的摻 雜物之可離子化的氣體。可離子化的氣體之例子係包含 BF3、％、Ar、PF5以及B2h6。質量流控制器38係調節氣 體被供應至該室10的速率。圖丨中所示的組態係提供連續 的處理氣體流在固定的氣體流速率以及固定的壓力之下。 該壓力以及氣體流速率最好是被調節以提供可再現的結果 〇 在動作中，晶圓20係被定位在平台14之上。接著， 該壓力控制系統、質量流控制器38以及氣體源36係產生 所要的壓力以及氣體流速率在室1〇中。舉例而言，該室 10可以用BF3氣體運作在10 mtorr的壓力之下。該脈衝源 30係施加一連串的高電壓脈衝至該平台14，而因此施加至 晶圓20 ’使得電漿40形成在晶圓2〇與陽極24之間。如 此項技術中所知的，該電漿40係包含來自氣體源36之可 離子化的氣體的正離子。該電漿40係更包含一電漿鞘42 在平台14的附近。在該高電壓脈衝的期間出現在陽極24 與平台14之間的電場係加速來自於電漿4〇的正離子橫跨 電槳鞘42而朝向平台Μ以及該晶圓20。被加速的離子係 被植入到晶圓20以形成雜質材料的區域。該脈衝電壓係被 11 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐） (請先閱讀背面之涑意事項再填寫本頁) I ---------訂------.--—線 經濟部智慧財產局員工消費合作社印製 472290 A7 B7 _ 五、發明說明（丨C ) (請先閱讀背面之注意事項再填寫本頁) 選擇以植入該些正離子至晶圓2〇中所要的深度。脈衝的數 目以及該脈衝持續期間係被選擇以提供在晶圓20中雜質材 料（該正離子）所要的劑量。每個脈衝的電流是脈衝電壓、 氣體壓力、氣體物種、以及該些電極之任意可變的位置之 函數。例如，該陰極至陽極的間隔可以爲了不同的電壓而 被調整。一個劑量處理器7〇係連接到電流量測元件50以 便於量測被累積到該目標晶圓20中之正離子的劑量。在一 種系統中，該些量測元件5〇係爲法拉第杯。如所知的，進 入該法拉第杯的正離子係在附接到該杯的電路中產生電流 。該電流係爲每個單位時間所接收的正離子數目、或是離 子電流的指不。 經濟部智慧財產局員工消f合作社印:t,1衣 在圖1中所示的電漿摻雜系統中，該平台14以及該 陽極24係爲平面的結構，亦即，本質上是平的。該陽極 24以及陰極14係分別大致上爲平面的結構，其可以具有 任何的形狀，例如，矩形、方形、圓形、等等，依據特定 的應用而定。該陽極24以及陰極14係彼此被間隔開一段 距離d，並且被配置以便於大致爲彼此平行的。如上所指 出地，該陽極24係可移動在該方向26上，以調整距離d 。如所知的，該距離d、在該室中的壓力、可離子化的氣 體之類型以及該高電壓脈衝的値與時序都是依據離子植入 所要的深度以及劑量來加以選擇的。 在本發明之第一實施例中，用於在例如是圖1的 PLAD系統中之植入，一個平面的陽極304係被設置相對 於一個平面的陰極3〇2，如圖2A與2B所示。該平面的陽 12 本紙張尺度適用中國國家標^(CNS)^4規格（210 X 297公釐） 經濟部智慧財產局員工消t合作社印製 472290 A7 , __________ B7 五、發明說明（q ) 極304與平面的陰極302係被配置爲彼此大致上平行的。 一個中空的圓柱形陰極300係被定位以實際上圍繞著介於 該平面的陽極304以及該平面的陰極302之間的空間。該 中空圓柱形陰極300是該陰極300的幾何形狀係封包或是 圍繞在其中的空間之意思的“中空”。該陰極本身並非是中 空的，因爲其係由被使用來製造用於PLAD系統之陰極所 知的材料所製成的，例如是固體的鋁或是塗覆矽之固體的 鋁。 在動作中，該平面的陽極304係典型地連接到一個參 考電壓Vref，例如是接地，而該圓柱形中空陰極300以及 該平面的陰極302兩者都被耦接至一個高電壓脈衝源30的 輸出。一電漿40係被形成在該平面的陽極304與該平面的 陰極3〇2之間、在該由該圓柱形中空陰極300所界定的容 積之內。在該高電壓脈衝的期間，來自電漿40的正離子係 被加速撗跨電漿鞘42而朝向該目標20。 本發明之第一實施例沿著如圖2A中所示的線2B-2B 之橫截面係被呈現在圖2B中。該圓柱形中空陰極300可 以實際上與該平面的陰極302分開、或是機構上被連接至 該平面的陰極3〇2。舉例而言，當該平面的陰極302被附 接至該中空陰極300時，該圓柱的一端係被封閉，此構成 一個“杯子”。該平面的陰極302可以電氣地耦接至尙未形 成一封閉的杯子之中空陰極300。 在動作中，該中空陰極係產生一更均勻的電黎並且容 許使用較低的氣體壓力。中空陰極放電係具有優點於習知 13 本紙張尺度適用中國國家標準（CNS)A4規袼（210 X 297公釐） -------------! 1 h I I I 訂---I-----J (請先閱讀背面之注意事項再填寫本頁) 472290 A7 B7 五、發明說明（π ) 的冷陰極放電，因爲對於特定的偏壓、氣體、氣體壓力以 及表面材料而言，該中空陰極已經被展示來產生高達100 倍甚至更高的平面陰極結構之電流密度。此“中空”陰極的 效應係使得電子來回地彈跳於該中空陰極3〇0的部分之間 ，以增加離子化以及離子電流。由於該電流是較大的，該 產出量也是較高的。或者是，較低的壓力係可被利用，It匕 導致相同的植入時間。在較低的氣體壓力下之運作也需要 較少的時間來抽真空並且接著再塡充該室，因爲在抽真空 之後，較少的摻雜物氣體必須被重新導入，因此導致增加 的產出量速率、在較低的氣體消耗之下。 在本發明之第二實施例中，如圖3 A中所示，該平面 的陽極304以及該平面的陰極302係被設置爲彼此大致上 平行的，並且爲彼此間隔開的，類似於圖2A中所示的組 態。一個矩形中空陰極3〇〇'係被設置以便於封包介於該平 面的陽極304以及該平面的陰極302之間的容積。第二實 施例沿著如圖3A中所示的線3B-3B之橫截面係被呈現在 圖3B中。爲了簡化解說，該電漿40以及電漿鞘42並未 顯示在圖3A與3B中。 本發明之第二實施例的矩形中空陰極3 0 01係容許該目 標晶圓20被置放在該平面的陰極302之上、或是在該矩形 中空陰極300'之任一壁上。又此外，一個目標晶圓20可以 被定位在該平面的陰極302之上，並且一或多個其它的目 標晶圓20也可以被定位在該矩形中空陰極300'之一壁或是 多個壁上。對於利用如圖3A與3B中所示的矩形中空陰極 14 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐） (請先閱讀背面之注意事項#填寫本頁) --裝 訂---------線 經濟部智慧財產局員工消f合作社印製 經濟部智慧財產局員工消货合作社印製 472290 A7 B7 五、發明說明（A ) 300,之電漿摻雜室，此種一次植入離子在超過一個目標晶 圓20中的能力係有肋於增加的產出量。 當然，雖然如圖2A與3A中所示之平面的陽極304以 及平面的陰極302係被描繪成圓形或是矩形，但是一般具 有此項技術者將會理解的是這些平面的結構可以是圓形或 是可以具有任意其它所要的形狀。類似地，雖然具有圓形 橫截面之圓柱形中空陰極300以及具有矩形橫截面的矩形 中空陰極300,已經被描述，但是一種具有例如是多角形、 多邊形、或是“D”橫截面的中空陰極可被使用。本質上’ 該中空陰極之任何造成該“中空陰極效應”的幾何形狀都可 以被使用。 本發明人已經判斷出該中空陰極的直徑係影響到植入 的均勻性。該直徑越小，則該均勻性越差。然而，若該中 空陰極的直徑太大，其功效也會降低。對於一特定的裝置 之最佳的直徑可以由一般具有此項技術者輕易地加以決定 ，而無需過度的試驗。應注意的是’該中空陰極相對於該 平面的陰極的直徑之比例在1.5至2的範圍內係提供可接 受的結果。此外，已經觀察到的是，該中空陰極的長度也 影響到均勻性以及運作。若太短時，該中空陰極效應不是 有效的並且均勻性是差的。若該中空陰極太長時’效率是 低的，因爲遠離該植入區域所產生的電漿係被浪費掉。直 徑對長度的比例是在2至5的範圍內以提供可接受的結果 〇 在本發明之第三實施例中，如圖4A中所示，一個環 15 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐） — — — — — — — — — — — I I · I I I l· ---< I I ----I I i (請先閱讀背面之注意事項再填寫本頁) 472290 經濟部智慧財產局員工消費合作社印製 A7 B7 五、發明說明（斗） 形陽極400係被設置在兩個平面的陰極302-1、302-2之間 的空間周圍。在動作中，陰極302-1、302-2係被連接至該 高電壓脈衝源30的輸出，而該環形陽極400被連接到一個 第二高電壓脈衝源130。在一個體現如圖4A中所示的結構 之電漿摻雜系統中，該可離子化的氣體係被帶至適當的壓 力，並且電漿係被產生在該等陰極302-1、302-2之間。有 利地，一或多個目標晶圓20可以被置放在該等陰極302-1 ’ 3〇2-2之上，以同時植入離子到多個目標之中。 如圖4A中所示的實施例之沿著線4B-4B的橫截面圖 係在圖4B中被呈現。如圖4B中所示，該電漿40係被產 生在該等陰極302-1、302-2之間，以助於離子植入到每個 目標晶圓20之中。 利用中空陰極的本發明之實施例的一種變化係在圖5 中以橫截面呈現。該陽極304係電氣地耦接至Vfef，而該 等中空陰極300、300’係電氣地耦接至該脈衝產生器30的 輸出。然而，該平面的陰極302係被耦接至一個第二高電 壓脈衝源130以接收一個植入電壓脈衝Vimp。此組態係提 供在該Pachen曲線之下的離子植入，如在該共同申請並且 共同擁有的申請案、與本發明同一日提出申請、名稱爲“用 於利用雙脈衝之低電壓電漿摻雜的方法與裝置”(代理人文 件號碼V0077/7085)中所描述，其內容係以其全體地被納 入於此。 習知地，PLAD系統係運作在一個被提供至該目標20 的負PLAD脈衝之下。如上參考圖1所示的，該室10以及 16 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐） (請先閱讀背面之注意事項再填寫本頁) • ^4 --------訂·------ 經濟部智慧财產局員工消費合作社印製 472290 A7 B7 五、發明說明（3) 該陽極24都被連接到接地。如圖6中所示，以正PLAD脈 衝運作現在是可行的。雖然在圖1中所述的系統中以正 PLAD脈衝運作是可行的，但是實際上施行是非常困難的 ，因爲整個室必須爲浮動的。根據如圖6中所示的實施例 ，該中空陰極300或是300'以及該室（未顯示)係被連接至 接地。第一與第二平面的陽極304-1、304-2係彼此相對地 被定位，其中該中空陰極被設置在其之間。一個正電壓脈 衝係被施加至該等平面的陽極3〇4-1、304-2。於是與前述 相同的植入過程係產生。有利地，在此實施例中，該電流 量測可以在該目標晶圓20爲接地之下輕易地被做成。在被 使用來量測該電流的法拉第杯之上將不會存在任何位移電 流，因而靈敏的電流量測方式係可以被利用。 本發明係利用一種中空陰極結構以便於改善在PLAD 系統中植入之均句度。該中空陰極可以具有數種幾何形狀 ，並且可以指定尺寸使得多個晶圓能夠一次被植入。 此增加的電流係起因於快速的次要電子(經由該陰極之 離子轟擊所產生)之陷獲(trapping)的緣故。因此，對於一特 定的植入電流（因而植入時間）以及偏壓電壓而言’該中空 陰極將容許使用在較低的氣體壓力下。由於該中空陰極“陷 獲”該快速的電子，因此更均句的電漿係被產生’因而更均 勻的植入輪廓係產生。 當利用本發明的中空陰極時，在低的植入電壓下（在 500伏特以下），一項在均勻性上的改善已經被量測。此均 勻性的改善係被量測爲大約是不具有中空陰極的PLAD系 17 I — — — — —----— II · I I I Γ I I I · I I I---1 I J- (請先閱讀背面之注意事項再填寫本頁) 本紙張尺度適用中國國家標準（CNS)A4規格（210x297公釐） 472290 A7 _B7 五、發明說明（) 統之5的倍數。此外，在植入速率之大約2或是更大的倍 數之增加係已被觀察到。 雖然已經加以顯示並且描述目前被認爲是本發明之較 佳實施例，但是明顯地對於熟習此項技術者而言各種的變 化以及修改可以在不脫離由所附的申請專利範圍所界定的 本發明之範疇下加以做成。 (請先閱讀背面之注意事項再填寫本頁) --裝·----^----訂---------線 經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家標準（CNS)A4規格（210 X 297公釐）472290 A7 B7 V. Description of the invention (丨) Field of the invention The present invention relates to a plasma doping system for ion implantation of a workpiece, and more specifically to a cathode geometry for a plasma doping system. shape. BACKGROUND OF THE INVENTION Ion implantation is a standard technique for introducing impurities that change conductivity into a semiconductor wafer. In a conventional ion implantation system, a desired impurity material is ionized in an ion source, the ion systems are accelerated to form an ion beam with a predetermined energy, and the ion beam system is directed The surface of the wafer. The active ion system in this beam penetrates into most of the semiconductor material and is embedded in the crystal lattice of the semiconductor material to form a region having a desired conductivity. Stringent requirements are imposed on ion-implanted semiconductors regarding the cumulative ion dose implanted into the wafer, implant depth, uniformity of dose across the wafer surface, surface damage, and unwanted contamination. Above the process. The implanted dose and depth determine the electrical activity of the implanted area, and dose uniformity is necessary to ensure that all components on the semiconductor wafer have operating characteristics within specified limits. Excessive surface damage ', especially chemical etching, or contamination of the surface may destroy previously fabricated structures on the wafer. In some applications, it is necessary to form a shallow junction in a semiconductor wafer ', wherein the impurity material is confined to a region near the surface of the wafer. In these applications, the high-energy acceleration of conventional ion implanters and the associated beam-forming hardware are not necessary. Therefore, it has been proposed that 3 paper sizes are applicable to the Chinese National Standard (CNS) A4 specification (2〗 〇 × 297 mm) (please read the precautions on the back before filling this page). Loading ----- r --- Order --------- Line Economy, Wisdom, and Production Bureau Staff Consumption Cooperative Printed 472290 A7 B7 V. Description of the Invention (-/) Use of a plasma for forming shallow junctions in semiconductor wafers Doping (PLAD) system. (Please read the precautions on the back before filling this page.) In a PLAD system, a semiconductor wafer is placed on a conductive platform in a chamber, and the platform functions as a cathode. An ionizable gas system containing the desired dopant material is introduced into the chamber 'and a local voltage pulse system is applied between the platform and the anode (or chamber wall). A plasma with a plasma sheath is generated near the wafer. The applied voltage is such that ions in the plasma pass through the plasma sheath and are implanted into the wafer. The depth of implantation is related to the voltage applied between the wafer and the anode. A plasma doping system is described in U.S. Patent No. 5,354,381 issued to Sheng on October 11, 1994. Printed by an employee cooperative of the Intellectual Property Office of the Ministry of Economic Affairs. In the PLAD system described above, the high-voltage pulse grandson generates the plasma and accelerates positive ions from the plasma toward the wafer. Among other types of plasma implantation systems, known as plasma source ion implantation (PSII) systems, another plasma source system is utilized to provide a continuous plasma. (These implant systems are also known for several other initials, the most common being plasma immersion ion implantation, PIII). In such a system, the platform and wafer are immersed in the continuous plasma, and a high voltage pulse system is applied between the platform and the anode at intervals, so that positive ions in the plasma are Accelerate towards the wafer. An example of such a system is described in U.S. Patent No. 4,764,394, issued to Conrad on August 16, 1988. One advantage of the PLAD system over the PSII system is that the plasma will only conduct when the target object is implanted. This is because the PSII system 4 standard is applicable to the continuous plasma of China's "Ticket Standard (CNS) A4 Specification (2. 丨 〇X 297 " ¥ " fat ~) 472290 A7 B7 V. Description of the Invention (>]) The reduction in the number of chemically active species produced thereby reduces chemical damage to the wafer surface. In addition, the continuous plasma may cause a high degree of implanted contaminants and a high degree of particulate formation. The PLAD system improves the PSII system by turning off the plasma except when the target object is biased to implant ions. This reduces the extent of contamination, fine particles, and surface etch damage. The PLAD system has a minimum breakdown voltage Vbd, below which the plasma system is activated so that ions can be implanted. The breakdown voltage Vbd is defined by the physical characteristics of the system, which includes the surface material of the cathode, the type of gas present in the system, the gas pressure P in the system, and the distance d from the cathode to the anode. For a specific surface material and gas type, the breakdown voltage curve Vbd is a function of P X d and is known as the Paschen curve. This process is fully described in the textbook of plasma physics. Typically, the smallest value of this breakdown voltage Vbd is close to Pd and 500 nanotorr-cm. For BF3, a common feed gas for PLAD for Si, the minimum breakdown voltages Vbd and -530V. Other dopant feed gas / substrate combinations will have similar minimum collapse voltages Vbd. In the conventional PLAD system, the implantation energy of ions in the plasma is directly proportional to the voltage from the cathode to the anode. In a PLAD system, the ionic current to the cathode is a function of the applied voltage, gas pressure, and surface conditions. For voltages close to Vbd, this current is low. When the voltage or the pressure is increased, the current is increased. In order to increase the current and thus reduce the implantation time, it is desirable to operate at higher pressures to withstand voltages exceeding Vbd. Area 5 (Please read the precautions on the back before filling out this page) —Packing ----- ^ — Order --------- Printed by the Consumer Goods Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs Chinese National Standard (CNS) A4 Specification (2) 0 X 297 mm) 472290 Employees of Intellectual Property Bureau of the Ministry of Economic Affairs, cooperation and printing Du A7 B7 V. Description of invention (W) Surface condition, surface temperature, material, material structure ( Crystalline vs. amorphous), etc., also play a relevant role in the area's ion current. To increase the production rate, that is, to increase the output of the target wafer through the doping process, the time spent processing each wafer needs to be reduced. As is known, the cycle time for a target wafer includes the time required to evacuate the chamber, the time required to introduce the dopant feed gas, and the chamber to the desired pressure, and the ion current The length of time required to bombard the target wafer to the extent required to achieve the desired dopant density. Therefore, a way is needed to improve the production rate and uniformity using a PLAD system. Summary of the Invention According to a first feature of the present invention, a pulsed plasma processing system is provided. The system includes an anode; a target cathode on which a first target is to be placed, the target cathode being spaced from the anode and positioned substantially parallel to the anode; and a hollow cathode, the system of which It is disposed adjacent to each of the anode and the target cathode. The hollow cathode is a portion of the space between the anode and the target cathode. The system further includes a first high-voltage pulse source having an output, wherein the anode system is coupled to a reference voltage; and the target cathode and the hollow cathode system are respectively connected to the output of the first high-voltage pulse source. In another feature of the invention, the system includes a first chirped voltage pulse source having a first output and a second high-voltage pulse source having a second output. The anode system is coupled to a reference voltage; the target cathode system is coupled to the second output; and the hollow cathode system is coupled to 6 paper sizes applicable to China National Standard (CNS) A4 (210 X 297 mm) (Chu) (Please read the notes on the back before filling this page) 丨 -----: ---- Order ---- 1 ---- line 472290 A7 B7 V. Description of the invention ($) An output. In another feature of the invention, a pulsed electrical processing system is provided. The system includes a casing; an anode disposed in the casing, the anode and the casing are coupled to a reference voltage; a target cathode, on which a first target is to be placed, the target A cathode system is disposed in the casing, spaced from the anode and positioned substantially parallel to the anode; one is disposed in the casing and adjacent to each of the hollows of the anode and the target cathode. The cathode, the hollow cathode is a part of the space surrounding the anode and the target cathode; and a high-voltage pulse source connected to the target cathode and the hollow cathode. In yet another feature of the invention, a method of implanting ions into a first target in a pulsed plasma processing system is provided. The method includes providing an anode; positioning a cathode spaced from the anode and being substantially parallel to the anode; setting the first target above the cathode; positioning a hollow cathode adjacent to the anode and the cathode 'And between the anode and the cathode; and applying a first high voltage pulse to the hollow cathode, wherein the hollow cathode surrounds a portion of the space between the anode and the target cathode. In still another feature of the present invention, a pulsed plasma processing system is provided, which includes a first anode; a second anode, which is spaced from the first anode and opposite to the first An anode; a hollow cathode disposed adjacent to the first and second anodes, the hollow cathode surrounding a space between the first and second anodes; and a first wide voltage pulse source Supply a positive voltage pulse with respect to a reference voltage 7 (Please read the precautions on the back before filling this page) Standards are applicable to China National Standard (CNS) A4 specifications (210 X 297 mm) Printed by the staff of the Intellectual Property Bureau of the Ministry of Economic Affairs and printed by the cooperative 472290 A7 B7 V. Description of the invention (b) Passed to each of these first and second anodes ; Wherein the hollow cathode is coupled to the reference voltage. Brief description of the drawings In order to better understand the present invention, the drawings are referred to, wherein the same reference numerals refer to the same elements, and in which: Figure 1 is the essential block diagram of a conventional plasma doping system Figure 2A is a schematic diagram of a first embodiment of the present invention; Figure 2B is a cross-section of Figure 2A taken along the line 2B-2B in Figure 2A; Figure 3A is a schematic view of a second embodiment of the present invention 3B is a cross-section of FIG. 3A taken along line 3B-3B in FIG. 3A; FIG. 4A is a schematic view of a third embodiment of the present invention; FIG. 4B is a line along FIG. 4A 4B-4B is a cross-sectional view of FIG. 4A; FIG. 5 is a cross-sectional view of the present invention using a double PLAD pulse; and FIG. 6 is a cross-sectional view of the present invention using a positive PLAD pulse. Brief description of some representative symbols at noon 10 Plasma doping chamber 12 Closed volume 14 Platform 20 Semiconductor wafer 8 (Jing first read the precautions on the back before filling this page) Installation ----- ^ --- Order ---- The size of the paper is applicable to China National Standard (CNS) A4 (210 X 297 mm). Employees of the Intellectual Property Bureau of the Ministry of Economic Affairs, Cooperative Cooperative Stamp ^ 290 290 A7 _B7__ 5. Description of the invention (1) 24 anode 26 arrow 30 high voltage pulse source 32 controllable valve 34 vacuum pump 36 gas source 38 mass flow controller 40 plasma 42 plasma sheath 44 pressure sensor 46 controller 50 measuring element 70 dose processor 130 second high voltage pulse source 300 hollow cylindrical cathode 300 'rectangular hollow cathode 302, 302-1, 302-2 plane cathodes 304, 304-1, 304-2 plane anodes 400 ring anodes Detailed description of one of the conventional plasma doping systems The example is shown schematically in FIG. 1. A plasma doping chamber 10 defines a closed volume 12. A platform (cathode) 14 positioned in the chamber 10 provides a surface for supporting a workpiece such as a semiconductor wafer 20. Semiconductor wafers are only possible. 9 This paper size is applicable to China National Standard (CNS) A ^ specifications (210 X 297 mm) (Please read the precautions on the back before filling this page). --------- Order ----- Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Online Economy 472290 A7 _ B7 V. An example of the target type of invention description (X). The invention is not limited to implanting ions only in semiconductor wafers. For example, ion implantation is also possible in metals, automotive components, dies, and plastics used as tools. For example, the wafer 20 may be clamped to the flat surface of the platform 14 at its periphery. This platform μ supports the wafer 20 and provides electrical connection to the wafer 20. In one version, the platform 14 is substantially planar and has an electrically conductive surface for supporting the wafer 20. In another version, the platform 14 includes conductive pins for electrical connection to the wafer 20. An anode 24 system is positioned in the chamber 10 in a spaced relationship from the platform (cathode) H. The anode 24 can be moved in a direction perpendicular to the platform 14 indicated by an arrow 26. The anode 24 is typically connected to the electrically conductive wall of the chamber 10, and both can be connected to ground. In one version, the anode 24 and the platform 14 are substantially parallel to each other. The wafer 20 and the cathode 14 are connected to a high-voltage pulse source 30, so the wafer 20 functions as a cathode. The pulse source 30 typically provides pulses in the range of about 100 to 10,000 volts, for a duration of about 1 to 50 microseconds, and below a pulse repetition rate of about 100 Hz to 2 KHz. It will be understood that these pulse parameters are only by way of specific examples, and other systems are available. The closed volume 12 of the chamber 10 is coupled to a vacuum pump 34 through a controllable valve 32. A gas source 36 is coupled to the chamber 10 through a mass flow controller 38. A pressure sensor 44 located in the chamber 10 provides a signal indicating a chamber pressure to a controller 46. The controller 46 compares the sensed chamber pressure with the desired pressure input, and provides 10 ---- Line '(Please read the precautions on the back before filling this page) This paper size is applicable to China National Standard (CNS) A4 (210 X 297 Gongchu) 472290 A7 ___ —--- B7_. DESCRIPTION OF THE INVENTION (i) A control signal to the valve 32. The control signal controls the valve 32 to minimize the difference between the pressure in the chamber and the desired pressure. The vacuum pump 34, the valve 32, the pressure sensor 44, and the controller 46 form a closed loop pressure control system. The pressure is typically controlled in the range of about 1 millitorr to about 500 millitorr, but is not limited to this range. The gas source 36 supplies an ionizable gas containing a desired impurity for implantation into the workpiece. Examples of ionizable gases include BF3,%, Ar, PF5, and B2h6. The mass flow controller 38 regulates the rate at which gas is supplied to the chamber 10. The configuration shown in Figure 丨 provides a continuous process gas flow at a fixed gas flow rate and a fixed pressure. The pressure and gas flow rate are preferably adjusted to provide reproducible results. In operation, the wafer 20 is positioned above the platform 14. Next, the pressure control system, mass flow controller 38, and gas source 36 generate the desired pressure and gas flow rate in the chamber 10. For example, the chamber 10 can be operated with BF3 gas under a pressure of 10 mtorr. The pulse source 30 applies a series of high-voltage pulses to the platform 14 and thus to the wafer 20 'so that the plasma 40 is formed between the wafer 20 and the anode 24. As is known in the art, the plasma 40 contains positive ions of an ionizable gas from a gas source 36. The plasma 40 further includes a plasma sheath 42 near the platform 14. The electric field appearing between the anode 24 and the platform 14 during the high-voltage pulse accelerates the positive ions from the plasma 40 across the electric paddle sheath 42 toward the platform M and the wafer 20. The accelerated ion system is implanted into the wafer 20 to form regions of impurity material. The pulse voltage is based on 11 paper sizes applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) (please read the intention on the back before filling this page) I --------- Order ------.--- Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 472290 A7 B7 _ V. Description of the invention (丨 C) (Please read the precautions on the back before filling this page) Select to implant The positive ions reach a desired depth in the wafer 20. The number of pulses and the duration of the pulses are selected to provide the desired dose of impurity material (the positive ion) in the wafer 20. The current of each pulse is a function of the pulse voltage, gas pressure, gas species, and any variable position of the electrodes. For example, the cathode-to-anode interval can be adjusted for different voltages. A dose processor 70 is connected to the current measuring element 50 to facilitate measuring the dose of positive ions accumulated in the target wafer 20. In one system, the measuring elements 50 are Faraday cups. As is known, the positive ions entering the Faraday cup generate a current in the circuit attached to the cup. The current is the number of positive ions received per unit time, or the value of the ion current. Employees of the Intellectual Property Bureau of the Ministry of Economic Affairs, cooperative cooperative seal: t, 1 In the plasma doping system shown in Figure 1, the platform 14 and the anode 24 are flat structures, that is, they are essentially flat in nature. . The anode 24 and the cathode 14 are substantially planar structures, which may have any shape, such as rectangular, square, circular, etc., depending on the specific application. The anode 24 and the cathode 14 are spaced apart from each other by a distance d and are arranged so as to be substantially parallel to each other. As indicated above, the anode 24 is movable in the direction 26 to adjust the distance d. As known, the distance d, the pressure in the chamber, the type of gas that can be ionized, and the chirp and timing of the high voltage pulse are all selected based on the desired depth and dose of the ion implantation. In the first embodiment of the present invention, for implantation in, for example, the PLAD system of FIG. 1, a planar anode 304 is set relative to a planar cathode 30, as shown in FIGS. 2A and 2B. . The paper size of this plane is 12 Chinese paper standard ^ (CNS) ^ 4 specifications (210 X 297 mm) Printed by the staff of the Intellectual Property Bureau of the Ministry of Economic Affairs Cooperative 472290 A7, __________ B7 V. Description of invention (q) pole 304 and the planar cathode 302 are arranged substantially parallel to each other. A hollow cylindrical cathode 300 is positioned to actually surround the space between the anode 304 on the plane and the cathode 302 on the plane. The hollow cylindrical cathode 300 is a "hollow" meaning that the geometry of the cathode 300 is a packet or a space surrounding it. The cathode itself is not hollow because it is made of a material known to be used to make cathodes for PLAD systems, such as solid aluminum or silicon-coated solid aluminum. In operation, the plane anode 304 is typically connected to a reference voltage Vref, such as ground, while the cylindrical hollow cathode 300 and the plane cathode 302 are both coupled to a high voltage pulse source 30 Output. A plasma 40 is formed between the planar anode 304 and the planar cathode 302 within the volume defined by the cylindrical hollow cathode 300. During this high-voltage pulse, the positive ion system from the plasma 40 is accelerated across the plasma sheath 42 toward the target 20. A first embodiment of the present invention is presented in FIG. 2B along a cross-section of line 2B-2B as shown in FIG. 2A. The cylindrical hollow cathode 300 may be physically separated from the planar cathode 302 or may be mechanically connected to the planar cathode 302. For example, when the flat cathode 302 is attached to the hollow cathode 300, one end of the cylinder is closed, which constitutes a "cup". The planar cathode 302 may be electrically coupled to the hollow cathode 300 which is not formed into a closed cup. In operation, the hollow cathode system produces a more uniform electrical connection and allows the use of lower gas pressures. Hollow Cathode Discharge System has advantages in the conventional 13 paper size applicable to Chinese National Standard (CNS) A4 (210 X 297 mm) -------------! 1 h III Order- -I ----- J (Please read the notes on the back before filling this page) 472290 A7 B7 V. Cold cathode discharge of invention description (π), because for specific bias, gas, gas pressure and surface material In terms of this, the hollow cathode has been shown to produce current densities of up to 100 times or more of a planar cathode structure. The effect of this "hollow" cathode is to cause electrons to bounce back and forth between 3,000 parts of the hollow cathode to increase ionization and ion current. Since the current is large, the output is also high. Alternatively, lower pressure systems can be used, and it results in the same implantation time. Operation at lower gas pressure also requires less time to evacuate and then refill the chamber, because after dosing, less dopant gas must be re-introduced, resulting in increased output Metering rate, at lower gas consumption. In the second embodiment of the present invention, as shown in FIG. 3A, the anode 304 of the plane and the cathode 302 of the plane are disposed substantially parallel to each other and spaced apart from each other, similar to FIG. 2A. The configuration shown in. A rectangular hollow cathode 300 ′ is provided to facilitate encapsulation of the volume between the anode 304 on the plane and the cathode 302 on the plane. The second embodiment is presented in Fig. 3B along the cross section of line 3B-3B as shown in Fig. 3A. To simplify the explanation, the plasma 40 and the plasma sheath 42 are not shown in Figs. 3A and 3B. The rectangular hollow cathode 3 01 of the second embodiment of the present invention allows the target wafer 20 to be placed on the planar cathode 302 or on any wall of the rectangular hollow cathode 300 '. In addition, one target wafer 20 can be positioned on the plane cathode 302, and one or more other target wafers 20 can also be positioned on one or more walls of the rectangular hollow cathode 300 '. on. For the use of rectangular hollow cathodes as shown in Figures 3A and 3B 14 This paper size applies Chinese National Standard (CNS) A4 (210 X 297 mm) (Please read the precautions on the back first # Fill this page)-Binding --------- Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, printed by the cooperative. Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, printed by the Consumer Goods Cooperative. 472290 A7 B7 V. Invention Description (A) 300, plasma doping chamber The ability to implant ions in more than one target wafer 20 at a time is costly in terms of increased throughput. Of course, although the plane anode 304 and the plane cathode 302 shown in FIGS. 2A and 3A are depicted as circular or rectangular, those skilled in the art will generally understand that the structure of these planes can be round The shape may have any other desired shape. Similarly, although a cylindrical hollow cathode 300 having a circular cross section and a rectangular hollow cathode 300 having a rectangular cross section have been described, a hollow cathode having, for example, a polygonal, polygonal, or "D" cross section Can be used. Essentially any geometry of the hollow cathode that causes the "hollow cathode effect" can be used. The inventors have determined that the diameter of the hollow cathode affects the uniformity of implantation. The smaller the diameter, the worse the uniformity. However, if the diameter of the hollow cathode is too large, its efficiency will be reduced. The optimum diameter for a particular device can be easily determined by those skilled in the art without undue experimentation. It should be noted that the ratio of the diameter of the hollow cathode to the diameter of the planar cathode in the range of 1.5 to 2 provides acceptable results. In addition, it has been observed that the length of the hollow cathode also affects uniformity and operation. If it is too short, the hollow cathode effect is not effective and the uniformity is poor. If the hollow cathode is too long, the efficiency is low because the plasma system generated away from the implanted area is wasted. The ratio of the diameter to the length is in the range of 2 to 5 to provide acceptable results. In the third embodiment of the present invention, as shown in FIG. A4 size (210 X 297 mm) — — — — — — — — — — — II · III l · --- < II ---- II i (Please read the notes on the back before filling this page) 472290 Printed by A7 B7, Consumer Cooperatives, Intellectual Property Bureau, Ministry of Economic Affairs 5. Description of the Invention (Bucket) The anode 400 is placed around the space between the cathodes 302-1 and 302-2 on two planes. In operation, the cathodes 302-1 and 302-2 are connected to the output of the high-voltage pulse source 30, and the ring anode 400 is connected to a second high-voltage pulse source 130. In a plasma doping system embodying the structure shown in FIG. 4A, the ionizable gas system is brought to an appropriate pressure, and a plasma system is generated at the cathodes 302-1, 302-2 between. Beneficially, one or more target wafers 20 may be placed on the cathodes 302-1 ' 30-2-2 to implant ions into multiple targets simultaneously. A cross-sectional view of the embodiment as shown in FIG. 4A along lines 4B-4B is presented in FIG. 4B. As shown in FIG. 4B, the plasma 40 is generated between the cathodes 302-1 and 302-2 to facilitate ion implantation into each target wafer 20. A variation of an embodiment of the invention utilizing a hollow cathode is presented in cross-section in FIG. 5. The anode 304 is electrically coupled to Vfef, and the hollow cathodes 300, 300 'are electrically coupled to the output of the pulse generator 30. However, the planar cathode 302 is coupled to a second high voltage pulse source 130 to receive an implanted voltage pulse Vimp. This configuration provides ion implantation under the Pachen curve, such as in the co-filed and co-owned application, filed on the same day as the present invention, and named "for low-voltage plasma doping using dual pulses. Miscellaneous Methods and Devices "(Agent Document No. V0077 / 7085), the contents of which are incorporated herein in their entirety. Conventionally, the PLAD system operates under a negative PLAD pulse provided to the target 20. As shown above with reference to Figure 1, the 10 and 16 paper sizes of this room are in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) (Please read the precautions on the back before filling out this page) • ^ 4- ------ Order · ------ Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 472290 A7 B7 V. Description of the invention (3) The anodes 24 are all connected to the ground. As shown in Figure 6, operation with a positive PLAD pulse is now feasible. Although it is possible to operate with a positive PLAD pulse in the system described in Figure 1, it is very difficult to implement in practice because the entire chamber must be floating. According to the embodiment shown in Fig. 6, the hollow cathode 300 or 300 'and the chamber (not shown) are connected to the ground. The anodes 304-1, 304-2 of the first and second planes are positioned opposite to each other, with the hollow cathode interposed therebetween. A positive voltage pulse is applied to the plane anodes 304-1, 304-2. Thus, the same implantation process as before is produced. Advantageously, in this embodiment, the current measurement can be easily made while the target wafer 20 is grounded. There will be no displacement current on the Faraday cup used to measure this current, so a sensitive current measurement method can be used. The present invention uses a hollow cathode structure to improve the average sentence degree of implantation in a PLAD system. The hollow cathode can have several geometries and can be sized so that multiple wafers can be implanted at once. This increased current results from the trapping of fast secondary electrons (produced by ion bombardment through the cathode). Therefore, for a specific implantation current (and therefore implantation time) and bias voltage, the hollow cathode will allow use at lower gas pressures. Since the hollow cathode "captures" the fast electrons, a more uniform plasma system is generated 'and a more uniform implant profile is generated. When using the hollow cathode of the present invention, an improvement in uniformity has been measured at low implantation voltage (below 500 volts). This improvement in uniformity was measured as a PLAD system without a hollow cathode. 17 I — — — — —----— II · III Γ III · II I --- 1 I J- (Please read first Note on the back, please fill in this page again.) This paper size applies the Chinese National Standard (CNS) A4 specification (210x297 mm) 472290 A7 _B7 V. Description of the invention () multiples of 5 times. In addition, increases in implantation rates of about two or more have been observed. Although it has been shown and described what is currently considered to be the preferred embodiment of the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention as defined by the scope of the appended patents Made under the category of invention. (Please read the precautions on the back before filling out this page) --Installation Applicable to China National Standard (CNS) A4 (210 X 297 mm)